Telephone systems are capable of transmitting digital information in a multiplicity of time division multiplexed channels, but the characteristics of such systems are such that the maximum rate at which digital data can be transmitted along any one channel is limited for example to 64 kbits per second.
It is an object of the present invention to provide a method of increasing the rate at which data can be transmitted by combining channels.
A public switched digital network cannot guarantee to provide from a multichannel source paths of equal delay to a multichannel destination. Additionally, crossovers may occur such that all the channels at the destination will not be connected to their corresponding channels at the source.
For effective data transmission at the increased rate, these delays need equalization and crossed connections need to be rearranged.
According to the invention, there is provided a digital data transmission system comprising a distributor for distributing the data in a data stream equally to N different outputs (where N is an integer), means for establishing N channels of communication between first and second locations, each channel for carrying the data from a corresponding one of said outputs from said first to said second location, and a reassembler at said second location to reassemble the distributed data received from said N channels into said data stream in its pre-distributed form.
According to the invention, there is further provided a method of transmitting a digital data stream comprising the steps of establishing N channels (where N is an integer) of communication from a first to a second location, transmitting synchronizing signals along each channel during an initial pre-data stream transmission period, reassembling the N streams received at the second location into a data stream, determining from said synchronizing signals in the reassembled data stream any differences in the transmission times along said channels, equalizing said transmission times, cyclically distributing the data into N streams, and transmitting each said stream along a corresponding one of said channels.